Known are several methods for imparting special characteristics to vacuum packages for food products; as an example, U.S. Pat. No. 3,792,181 which issued on Feb. 12, 1974 to Reid A. Mahaffy et al. discloses a container of a semirigid plastic material shaped to accommodate a detachable lid.
This prior container, while affording definite advantages, requires a shape as close and as similar as possible to the shape and dimensions of the product to be placed therein and thus it lacks desired versatility. An improvement on this packaging technique has been achieved by arranging articles to be packaged onto a supporting sheet-like material, which is then covered with a polymeric film; and thereafter, the volume included between the film, sheet-like material, and product is sealed by application of a pneumatic vacuum.
Such approaches, e.g., as described in U.S. Pat. No. 3,694,991 which issued Oct. 3, 1972 to Richard R. Perdue et al. need improvement as regards loading of the products into the package supporting sheet number, because its arrangement on such a sheet-like material prevents the product from being directly and definitively seated, and there may occur instances of improper arrangement of articles inside the packages.
Another problem, pointed out in detail in Italian Patent Application No. 21030 A/82 filed Apr. 30, 1982 by W. R. Grace & Co. (E. Bartolani et al., inventors) arises from the formation of folds in the film, especially along the vertical corners of the product being packaged.
The problem is further aggravated where, as is usual, the products to be packaged are arranged side-by-side on a web of sheet-like material for simultaneous packaging of several products preliminarily to subsequent severing of the sheet-like material to separate the individual packages.
In that case, on account of the cited folds spanning considerable distances, it often occurs that the sheet-like material is severed at areas affected by said folds, thus causing air to seep into the packages.
It should be also considered that the upper film has areas particularly weakened in the proximities of the areas of connection to the sheet-like material, which are due to the high stretch to which the film is subjected during the packaging step.
In the light of the foregoing technical problems, it is a primary object of this invention to remove such prior drawbacks by providing a method of vacuum packaging which can eliminate the dimensional dependence of the container on the product it must accommodate.
Another important object of the invention is to provide a method which can combine good aesthetic characteristics with ease of loading the product during the packaging step, attenuation of the folds in the upper film with full elimination of their damaging effect and considerable strengthening of the package, which is apt to facilitate its handling and avoid deformation of the package under the action of the applied vacuum.
A further object of the invention is to provide an apparatus to implement the above method.
It is another object of this invention to provide a vacuum package having no voids in its interior.
In addition, an object of the invention is to provide a vacuum package with enhanced properties of presentation and outward appeal of the packaged product.
Yet another object of this invention is to provide a vacuum package of low cost and great convenience, and, above all, one combining all of the advantages set forth hereinabove.